Abstract: A chiller system (10) includes a compressor (12), a condenser (14), a cooler (20), a bubbler tube (22) and a float valve (18) within the condenser (14). A solenoid valve (26) is disposed within the bubbler tube (22) and is adapted to selectively open and close the float valve (18) such that a refrigerant flow to the cooler (20) is throttled. The throttled refrigerant flow results in a reduction in system pressure which further results in a higher viscosity oil delivery to the compressor (12) by an oil management system (30).

Abstract: A refrigerant system operates with tandem compressors (22, 24). A control (41) for the refrigerant system is operable to change the capacities of each of the compressors dependent upon a load on the system. The control determines the percentage of maximum load capacity currently being utilized by each of the compressors. A compressor with the highest percentage is decreased in capacity should the control determine that excess capacity is being provided. Conversely, the control will increase the capacity of a compressor having a lower percentage, if insufficient capacity is being provided to meet a load on the system.

Abstract: A multi-rotor screw compressor includes a compressor housing defining at least three parallel rotor housing sections, each rotor housing section containing a rotor, and adjacent rotors defining at least two compressor pairs, the housing further including a suction port and a discharge port for each of the compressor pairs, and further including at least two additional ports selected from the group consisting of first closed lobe ports, last closed lobe ports, and economizer ports, wherein at least one of the additional ports is communicated with a first pair of the at least two pairs, and another of the additional ports is communicated with a second pair of the at least two pairs whereby interaction between the additional ports is reduced.

Abstract: A screw compressor includes a compressor housing defining parallel rotor housing sections, each rotor housing section containing a rotor, and adjacent rotors defining compressor pairs, the housing further including a suction port and a discharge port for each of the compressor pairs, and further including additional ports selected from first closed lobe ports, last closed lobe ports, and economizer ports, wherein at least one of the additional ports is communicated with a first pair of the at least two pairs, and another of the additional ports is communicated with a second pair of the at least two pairs whereby interaction between the additional ports is reduced. In accordance with a further aspect of the invention, configurations are provided so that the first discharge port has a lower volume index ratio (Vi) than the second discharge port.